It is often necessary to switch a field-effect transistor (FET) ON and OFF at high speeds with a driver circuit. It is common for such driver circuits to have a totem pole output which includes a "source" transistor for sourcing current to the gate of the FET and a "sink" transistor for removing charge from the gate of the FET. The source and sink transistors may respectively be considered to be part of active pullup and pulldown circuits.
It is undesirable for both pullup and pulldown circuits to be ON simultaneously (the cross-conduction condition), for then a relatively large current will flow from the power supply, through the pullup and pulldown circuits, and to ground, thereby wasting energy and causing unwanted heating. Therefore, if the driver circuit has already switched ON the FET in which the pullup circuit is ON and the pulldown circuit is OFF, then when switching OFF the FET it is desirable that the pullup circuit be switched OFF before the pulldown circuit is switched ON. Similarly, if the driver circuit has already switched OFF the FET in which the pulldown circuit is ON and the pullup circuit is OFF, then when switching ON the FET it is desirable for the pulldown circuit be switched OFF before the pullup circuit is switched ON.